Method and apparatus for separating gaseous mixtures



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METHOD AND APPARATUS FOR SEPARATING GASEoUs MIXTURES original Filed Aug.16, 1957 6 sheets-Sheet 2 m no INVENTORS CLARENCE J. SCHILLING LILBURNCARROLLCLAITOR BY A @mail ATTORNEYS July 3, 1962 c. J. SCHILLING ETALRe. 25,193

METHOD AND APPARATUS FOR SEPARATING GAsEous MIxTUREs Original Filed Aug.16, 1957 6 Sheets-Sheet 3 INVENTORS CLARENCE J. SCHILLING LILBURNCARROLL CLAITOR BY MAW ATTORNEYS July 3, 1962 c. J. scHlLLlNG ETAL Re25,193

METHOD AND APPARATUS FOR SEPARATING GASEOUS MIXTURES Original Filed Aug.16, 1957 6 Sheets-Sheet INVENTOR` CLARENCE J. SCHILLING LI LBURN CARROLLCLAITOR ATTORNEYS July 3, 1962 c. J. scHlLLlNG ETAI. Rev25,193

METHOD AND APPARATUS FOR SEPARATING GAsEoUs MIXTURES Original Filed Aug.16. 1957 6 Sheets-Sheet 5 INVENTORS CLARENCE J. scH|LL|NG Ll LBURNCARROLL CLAITOR ATTORNEYS July 3, 1962 c. .1. scHlLLlNG ETAL Re. 25,193

METHOD AND APPARATUS FOR SEPARATING GASEOUS MIXTURES Original Filed Aug.16, 1957 6 Sheets-Sheet 6 rc2 J ASL j g Q I'O E] INVENTORS CLARENCE J.scHlLLlNs E1n( 9 LILBURN cARRoLLcLAlToR ATTORNEYS United States Patent OMETHOD AND APPARATUS FOR SEPARATING y Matter enclosed in heavy bracketsappears in the original patent but forms no part of this reissuespecification; matter printed in italics indicates the additions made byreissue.

This invention relates to improvements in the separation of gaseousmixtures by a low temperature fractionating operation and moreparticularly to methods of and apparatus for removing from thefractionating operation high boiling point impurities introduced intothe operation with the gaseous mixture.

It is known that high boiling point impurities present in `gaseousmixtures must be removed or reduced to comprise an insignificantpercentage of the gaseous mixture in order to prevent difficulties inthe operation of low temperature fractionating cycles. For example, inthe separation of air into oxygen and nitrogen components, the normalcontent of carbon dioxide in the air feed to the cycle precipitates andcollects in the cycle, especially in the colder portions of the cycle,and affects operation of the cycle and eventually requires the cycle tobe shut down for `defrosting. In order to obtain substantiallycontinuous operation it is necessary to remove substantially the totalcarbon dioxide entering the cycle with the air feed. Also it isnecessary to provide means for removing from the cycle other highboiling point components of the air feed, particularly hydrocarbonswhich, when concentrated in the cycle, constitute serious explosionhazards.

Several methods have been employed in the past for removing high boilingpoint impurities from gaseous mixtures, such as the removal of carbondioxide from air.

In one method the air feed prior to its entry into the With a causticsolution for example, to remove the carbonk dioxide. This methodrequires bulky equipment and materially increases the initial andoperating costs. Another method attempts to remove the carbon dioxideyby low temperature precipitation. This is accomplished -by the use ofswitching heat exchange zones of the regenerator or recuperative type bywhich the stream of incoming compressed air is cooled to a temperaturebelow the precipitation temperature of carbon dioxide in heatinterchange with a stream of relatively cold product of thefractionating operation. The carbon dioxide precipitated from the airfeed collects in one passageway of the heat exchange zone and when theheat exchange zone is switched the product gas is caused to flow throughthe passageway in which the carbon dioxide has deposited, countercurrentto the direction of flow of the air feed therethrough, to sweep out thecarbon dioxide deposits.

Due to the difference of theispecitic heat of high pressure air Iand lowpressure product gases at low temperature, means must be provided tounbalance the heat exchange zone in order to substantially completelyremove carbon dioxide deposits -by the outowing product stream. Even incycles employing unbalanced heat exchange zones, particles of carbondioxide are entrained in the air feed owing from the heat exchange zoneand Y accumulate at some point in the cycle producing malfunc- ICC itions and eventually requiring shutdown for defrosting. In addition,switching type heat exchange devices are expensive to manufacture andthe required switclnng presents mechanical and operational diiculties.

In copending application of Clarence I. Schilling and Clyde McKinley,Serial No. 576,963, tiled April 9, 1956 for Method and Apparatus forSeparating Gaseous Mixtures Including High Boiling Point impurities, nowPatent No. 2,968,160, there is disclosed an arrangement forsubstantially completely removing from a fractionating cycle highboiling point impurities introduced into the cycle with the feed mixturewithout employing chemical scrubbing or switching heat exchange zones.According to the method and apparatus disclosed and claimed in thiscopending application, gaseous feed mixture enters the cycle under apredetermined relatively high pressure and is cooled in heat exchangeeffecting relation with cold product gas without precipitation of highboiling point impurity in the passageway of a non-switching heatexchange zone and the stream is then expanded to a relatively lowpressure, such as a pressure as exists in the fractionating zone, toestablish the pressure and temperature Conditions for precipitation ofhigh boiling point impurity. The expanded gaseous mixture includesprecipitated high boiling point impurity and high boiling point impuritydissolved in the gaseous mixture. A uid stream including substantiallythe total high boiling point impurity of the gaseous mixture is formedfrom the stream of expanded gaseous mixture and passed through filterand adsorber zones to substantially completely remove high boiling pointimpurity therefrom. Precipitated high boiling point impurity issubstantially removed in the iilter zone, While high boiling pointimpurity dissolved in the Huid stream and precipitated high boilingpoint impurity that may How through the filter zone are removed in theadsorber zone. From the adsorber zone the lluid stream is fed to afractionating zone for low temperature separation. e

In one type of fractionating cycle constructed in accordance with theprinciples of the Schilling and McKinley application discussed above,expanded gaseous feed mixture is fed to the high pressure zone of a twostage fractionating column and the liuid stream passed through thefilter and adsorber zones comprises a stream of liquid fractionwithdrawn from the base of the high pressure section, such as a streamof liquid crude oxygen in the case of the separation of air. It has beendiscovered that in this type of cycle certain physical characteristicsof the feed mixture are critical with respect to the percentage of thetotal high boiling point impurity contained in the fluid stream passedthrough the iilter and adsorber zones. In particular, in a cycle of theabove type in which a portion of the feed mixture is expanded with workin order to provide refrigeration required to produce a liquid product,it /has been determined that a substantial portion of the high boilingpoint impurity precipitates on the lower fractionating tray or trays ofthe high pressure zone and alects fractionating efliciency. It isbelieved that this undesirable performance results from the fact thatthe effluent from the expansion engine comprises superheated vapor andthat the high boiling point impurity contained in the superheated vaporis not cooled to precipitation temperature prior to contact with thelower fractionating tray of the high pressure zone or prior to reachinga region adjacent the lowermost fractionating tray.

It is an object of the present invention to provide a novel method andapparatus which solves the foregoing problem. t

Another object is to provide a novel method and apparatus for removinghigh boiling point impurities from a fractionating operation.

Still another object of the present invention is to provide a novelmethod of and `apparatus for removing high boiling point impurities froma fractionating cycle in which the gaseous feed mixture is cooled todifferent relatively low temperatures.

In general, according to the principles of the present inventionsubstantially the total high boiling point impurity may be removed fromgaseous feed mixture through the use of filter and adsorber zones byconditioning the gaseous feed mixture in a novel manner to insure thatsubstantially the total high boiling point impurity is precipitated ordissolved in a iiuid that may comprise a portion of the gaseous feedmixture or a iiuid including components of the gaseous feed mixture. Therequired conditioning of gaseous feed mixture may be accomplishedaccording to the present invention by intermixing portions of thegaseous feed mixture at different relatively low temperatures, or byintermixing the total gaseous feed mixture or a portion of the gaseousfeed mixture with a iiuid including components of the gaseous feedmixture, or by a combination of separation and intermixing steps.

Other objects and features of the present invention will appear morefully below from the following detailed description considered inconnection with the accompany- .ng drawings which disclose severalembodiments of the nvention. It is to be expressly understood that thedrawngs are designed for purposes of illustration only and 1ct as adefinition of the limits of the invention, refer- :nce for the latterpurpose being had to the appended :lai-ms.

-In the drawings, in which similar reference characters lenote similarelements throughout the several views:

FIGURE 1 is a diagrammatic illustration of a frac- :ionating cycleembodying the principles of the present nvention;

FIGURE 2 is a diagrammatic view of anotherfem- Jodirnent of the presentinvention;

FIGURE 3 is an enlarged view, partially in section, )f a device includedin the cycle shown in FIGURE 2;

FIGURE 4 is a view in section taken along the line l-4of FIGURE 3;

FIGURE 5 is a view in section taken along the line --S of FIGURE 3;

FIGURE 6 is a diagrammatic view of a fractionating :ycle constructed inaccordance with another embodinent of the present invention;

FIGURE 7 is a diagrammatic showing of still another mbodiment of thepresent invention, and

FIGURE 8 is a diagrammatic illustration of a fracionating cycleembodying further features of the present avention.

With reference more particularly to FIGURE 1 of he drawings, afractionating cycle embodying the priniples of the present invention isdisclosed therein for eparating low-boiling components of gaseousmixtures ncluding higher boiling point impurities. Gaseous feed mixture,such as atmospheric air under superatmospheric ressure and substantiallyfree of moisture, enters the ycle through conduit 10 and is conductedthereby to ath 11 of heat exchange device 12 for `heat exchange ffectingrelationship with cold product of a fractionating peration described indetail below. A first stream of aseous feed mixture, comprising aportion of the 'total aseous mixture, isV withdrawn from the path I11 bya onduit \13 and conducted thereby to an expansion engine 4 wherein thefirst stream of the gaseous mixture is ex- `anded with the production ofwork to a relatively low' uperatmospheric pressure. The iirst stream ofgaseous iixture is withdrawn from the path 11 at a tempera- 1re suchthat liquid does not form in the expansion enine 14 and the eiiluentfrom the expansion engine inthe onduit l1S is cooled to a temperaturewithin the supereat region at the relatively low pressure. The temperainthe gaseous mixture, such as carbon dioxide in the case of air feed, andthe superheated vapor from the expansion engine includesgaseous highboiling point impurities. A control valve y16 is provided'in the conduit13 to determine the percentage of the total feed mixture passed to theexpansion engine. The remaining portion of the feed mix-ture, or secondstream of feed mixture, flows through the path 11 and emerges from thecold end of the heat exchange device 12 in conduit 17 at a temperatureslightly above saturation temperature at the existing pressure and isthen expanded in valve 18 to a relatively low superatmospheric pressurecorresponding to the pressure of the effluent from the expansion engine.The second stream of the feed mixture upstream of the expansion valve 18is above a critical pressure so that highV boiling point impuritiesremain Yin gaseous phase, however the pressure and temperatureconditions downstream of the expansion valve are such that high boilingpoint impurities precipitate and a portion of the feed mixture'smay beliquefied.

In accordance with the principles ofthe present invention, the firststream of superheated gaseous mixture from the expansion engine iscooled to a temperature at least corresponding to the precipitationtemperature of the high boiling point impurities at the existingpr-essure in order to concentrate substantially the total high boilingpoint impurity of the total feed mixture in a fluid stream for passageto filter and adsorber zones. This is accomplished in the embodiment ofthe invention shown in FIGURE l by intermixing the first and secondstreams of feed mixture in such a manner as to concentrate substantiallythe total high boiling point impurity in the liquid portion of the feedmixture. The intermixing may or may not comprise a heat interchangeresulting in the total gaseous mixture being at a substantially uniformtemperature, such as saturation temperature, depending at least in partupon the precipitation temperature of the high boiling point impurities.As shown in FIGURE 1, the conduitsl I15 and 19 feed the first and secondstreams of gaseous mixture to the base of a conglomerator 20 f whichcomprises a closed vessel including a liquid outlet conduit 21 and avapor outlet conduit 22. The liquid outlet conduit 21 communicates withthe vessel at a medial level dividing the vessel into ar lower liquidreceiving chamber 23 and an upper vapor receiving chamber 24.

The size of the liquid receiving chamber 23 is designed so that vaporentering the chamber 24 is substantially free of high boiling pointimpurity. As mentioned above,

vapor entering the chamber 24 may be at a temperature above thetemperature of the liquid in the chamber 23 or the vapor and liquidwithdrawn from the conglomerator may be at a substantially uniformtemperature, such a saturation temperature depending in part upon theprecipitation temperature of the high boiling point impurities in thegaseous mixture. In any event, the vapor portion withdrawn from theconglomerator in the conduit 22 is substantially free of high boilingpoint impurities and substantially the total high boiling pointimpurities are concentrated in the liquid portion withdrawn through theconduit 2'1, either as precipitated high boiling point impurity or ashigh boiling point impurity dissolved in the liquid portion. Theconduits 21 and 22 are connected to a conduit 25 and the total feedmixture is fed thereby to a high pressure section 30 of a two-stagef-ractionating column 31 which may be of conventional constructionincluding a low pressure section 32 and a refluxing condenser 33, thehigh pressure section 30 and the low pressure section 32 being providedwith suitable liquid-vapor contact means such as fractionating trays 34.The .feed mixture undergoes preliminary separation in the high pressuresection 30 producing a high boiling point liquid fraction collecting ina pool 35 in the base of the column and a gaseous low boiling pointfraction 1re of the expansion engine eiuent may be above the 75 whichlows upwardly into the refluxing condenser 33,

and is liquefied therein in heat exchange effecting relation With liquidhigh boiling point component collecting in a pool 36 in the base of thelow pressure section and surrounding the tubes of the refluxingcondenser. Liquetied low boiling point fraction flows downwardly fromthe reuxing condenser with a Dart entering the low oressure section asreux and with another part being collected in a pool 37 below therefluxing condenser from which a stream is withdrawn by conduit 38,expanded in valve 39 and introduced into the upper end of the lowpressure section as reflux. A stream of liquid high boiling pointfraction is withdrawn from the pool 35 by way of a conduit 40 as feedfor the low pressure section. As described in the copending applicationof Clarence J. Schilling and Clyde McKinley discussed above, the streamof high boiling point liquid fraction is passed in series throughlteriand adsorber zones and then expanded and introduced into the lowpressure section. As shown in the drawings, the conduit 4t) is connectedthrough switching valves 41 and 42 to lters 43'and 44. The filters areconnected by conduits 45 and `46 to .absorbers 47 and 4S, respectively,and the adsorbers are connected through switching valves 49 and 56 to aconduit 51 communicating with the low pressure section. An expansionvalve 52 is included in the conduit 51 for reducing the pressure of thestream of high boiling point fraction to correspond to the pressure ofthe low pressure section. Upon operation of the switching valves 41, 42,y49 and 50, the stream of liquid high boiling point fraction is causedto iiow serially through filter 43 and adsorber 47 or serially throughfilter 44' and adsorber 48 on its way to the low pressure section. Highboiling point impurity is substantially removed from the stream ofliquid high boiling point fraction upon flowing through afilter-adsorber combination. Precipitated high boiling point impurity issubstantially completely removed in the lters 43 or 44 and the adsorbers47 and 48 substantially completely remove high boiling point impuritydissolved in the liquid as well as particles of precipitated highboiling point irnpurity that may pass through the filters. The lter-adsorber combinations are provided in duplicate so that upon operation ofthe switching valves 41, 42, 49 andV 50 one combination is onestreanlWhile the other combination is off-stream for reactivation and purgingoperations. The latter operations may be accomplished according to theprinciples of the copending application by flowing a warm uid stream,such as a stream of Warm product gas, from conduit 53 to the conduit 45or the conduit -46 depending upon the position of the control valves 54and 55. The purging stream thus flows through the filters 43 or y44 incountercurrent relation with the stream of high boiling point fractionand leaves the cycle through outlet conduits '56 or y57 provided withcontrol valves 58 and 59y respectively, and flows through the adsorbers47 or 48 in concurrent relation with the stream of high boiling pointfraction and leaves the cycle through outlet conduits 60 or 61 providedwith control valves 62 and 63.

Separation of the `gaseous mixture is completed in the low pressuresection producing high boiling point component collecting in liquidphase in the pool 36 and low boiling point component which ows upwardlyinto the dome of the fractionating column and is withdrawn therefrom byway of a conduit 65. The conduit 65 conducts -a stream of low boilingpoint component to the cold end of path 66 of the heat exchange device12 wherein the low boiling point component is warmed in countercurrentheat exchange effecting relation with incoming feed mixture in the path11, the warmed stream leaving the cycle by way of a conduit 67 atsubstantially ambient temperature and atmospheric pressure. High boilingpoint cornponent may be withdrawn fromI the column in liquid phase byway of `a conduit l68 provided with -a control valve 69, or a part ofthe high boiling point component may be delivered in gaseous phase byway of a conduit 7 0 which communicates with path 71 of the heatexchange device 12 wherein theV stream of gaseoushigh boiling pointcomponent flows in countercurrent heat Yexchange effecting relation Withincoming feed mixture and is warmed and leaves the cycle by way of aconduit 'i2 at substantially atmospheric pressure and ambienttemperature.

The total gaseous mixture entering the high pressure section 30 throughthe conduit 25 is partly in liquid phase and partly in vapor ph-ase withsubstantially the total high boiling point impurity being concentratedin the liquid portion of the feed mixture, either as precipitated highboiling point impurity or as dissolved high boiling point impurity, dueto the action of the conglomerator 20 as described above. Uponintroduction of the feed mixture into the low pressure section theVliquid portion mixes with the liquid in the pool 35 and substantiallythe total high boiling point impurity collects in the liquid low boilingpoint fraction and is subsequently removed from the cycle by the -actionof the filter-adsorber cpmbinations as discussed above. Vapor flowingupwardly toward the fractionating plates o-f the high pressure sectionis substantially free of high boiling point impurity and thefractionating trays remain substantially free of precipitated highboiling point impurity. The foregoing performance may be obtained byintroducing the feed mixture into theA high pressure column above thepool 35 or beneath the liquid high boiling pointfraction as shown in thedrawing.

In operation of the cycle shown in FIGURE l, for separating air intooxygen and nitrogen components, dry air under a pressure about3000p.s.i.g. enters the cycle through the conduit 10 with a portion ofthe air feed flowing through the path 11 in countercurrent heat exchangeeffecting relation with cold nitrogen product =and emerging from thepath 11 at a temperature of about 245 F. In the expansion valve 19 theair feed is expanded. to about 85 p.s.i.g. with a concomitant drop intemperature to yabout 278 F. and partial liquefaction takes place. Sincethe pressure of the air feed is above about 550 p.s.i.g. the air feedleaving the cold end of the heat exchanger 12 is abovey theprecipitation temperature of carbon dioxide, however, the temperatureand pressure conditions existing downstream of the expansion valve 19are such that carbon dioxide precipitates. The remaining portion of theair isv withdrawn from the path 11 at about 100 F. and is expanded inthe expansion engine \14 to about 85 p.s.i.g. and cooled to atemperature of about 190 F. Thus the etiluent from the expansion enginecomprises superheated vapor including gaseous carbon dioxide. Thestreams of air feed are introduced into the conglomerator wherein carbondioxide is precipitated from the superheated vapor and substantiallythetotal carbon dioxide is concentrated in the liquid portion of the aireither as precipated carbon dioxide or as dissolved carbon dioxide.Inasrnuch as carbon dioxide under 85 p.s.i.g. first precipitates at atemperature of about 215 F., it is only necessary to cool thesuperheated vapor to below this temperature and not to saturationtemperature of about 280 F. Ihe combined air feed is introduced into thehigh pressure section with substantially the total carbon dioxide beingconcentrated in the liquid high boiling point fraction, crude oxygen,and subsequently removed therefrom upon -ilowing the feed to the lowpressure section through the Ifilter-adsorber combinations. Of course,other high boiling point components, such as hydrocarbons, are removedfrom the air feed along With the carbon dioxide.

In the embodiment off the invention shown in FIGURE 2 of the drawings,feed mixture introduced into the fractionating column is either ingaseous phase substantially free of high boiling point impurity or isfirst passed through filter and adsorber zones to remove substantiallythe total high boiling point impurity therefrom. As shown, superheatedfeed mixture from the expansion engine l14 including gaseous highboiling point impurity and `the remainder of the feed mixture in liquidand vapor phase and containing precipitated and dissolved high boilingpoint impurity are fed bythe conduits 16 and 19 to a conglomerator 80which functions to separate the feed mixture into a. vapor portionsubstantially free of high boiling point impurity and a liquid portioncontaining substantially the total high boiling point impurity. Withparticular reference to FIGURES 3, 4 and 5, the conglomerator 80 maycomprise a closed vessel 81 of circular cross-section having a liquidoutlet conduit 82 connected to the vessel at an intermediate level todivide the vessel into a lower liquid receiving chamber `at 83 and auupper vapor receiving chamber 84. The conduits 16 and 19 entering thebase of the vessel may terminate in closed ends 85 and may be providedwith =a series of openings 86 along their under sides for the dischargeof feed mixture therefrom. The upper end of the vapor receiving chamber84 is defined by a conical wall 87 which also forms the bottom wall of aseparating chamber 88 located -at the upper end of the vessel. A conduit8-9 is joined to the apex of the conical wall 87 and extends downwardlyinto the liquid receiving chamber 83 and terminates at an end 90.adjacent the bottom of the vessel. The vapor receiving chamber 84communicates with the separating chamber 88 by a conduit 91 having oneend 92 communicating with the vapor receiving chamber and an upper end93 being tangentially connected to the sidewall of the vessel formingthe upper portion of the separating chamber.

With this construction vapor flows tangentially into the separatingchamber and follows circular paths therein as shown by `arrows 94 inFIGURE 4. A vapor outlet con duit 95 extends into the upper end of thevessel 81 and downwardly into the `Separating chamber 88 and terminatestherein at end 96 below the discharge end 93 of the conduit 91. Inoperation, the liquid receiving chamber 83 irs filled with liquefiedfeed mixture and the superheated vapor introduced through the conduit 16is cooled to effect precipitation of high boiling point impurity. Vaporsubstantially free of high boiling point impurity is conducted fromchamber 84 to the separating chamber wherein entrained liquid isseparated and returned to the liquid receiving chamber through theconduit 89. Gaseous mixture in vapor phase and substantially free ofhigh boiling point impurity is discharged from the conglomerator throughthe conduit 95, and gaseous mixture in liquid phase containingprecipitated and dissolved high boiling point impurity flows through theconduit 82.

As shown in FIGURE 2, -the conduit 95 'feeds the vapor portion of thegaseous mixture into the high pressure section 30, either above the poolof liquid high boi-ling point fraction or into the pool as shown. Theliquid portion of the gaseous mixture is conducted by a conduit 97 andmerged with a stream of liquid high boiling point fraction withdrawnfrom the pool 35 and the combined streams are passed by the conduitthrough one of the filter-adsorber combinations 43`-47 or 44-48,expanded in valve 52and introduced into the low pressure section 32. Inthis cycle the vapor portion of the gaseous mixture introduced into thehigh pressure section by the conduit 95 is substantially free of highboiling point impurity and substantially the total high boiling pointimpurity introduced into the cycle with the feed mixture owing throughthe conduit 10 is removed by the filters 43, 44 and the adsorbers 47,48.

vIn the modification of the invention shown in FIG- URE 6 of thedrawings, an arrangement is provided for utilizing liquid high boilingpoint fraction from the high pressure section of the column as part ofthe liquid intermixed with the superheated vapor portion of the gaseousmixture. As shown, a stream of high boiling point liquid fraction isWithdrawn from the pool 35 in the base of the high pressure section byconduit 100 `and conducted thereby to `an injector 101 having itsdischarge `.feeding the liquid collecting chamber of the conglomerator80. Conduit 19 is connected to the nozzle 102 of the injector to provideIpropellant therefor. The liquid withdrawal conduit 82 of theconglomerator is connected by a conduit 103 to the filters 43 or 44dependingl upon the position of switching valves 41 and 42. Gaseousmixture in vapor phase is conducted by the conduit 95 to the highpressure section of the column. In operation of this cycle the liquefiedportion of the feed mixture as well as liquid high boiling pointfraction withdrawn from the high pressure section of the column is fedto the conglomerator and utilized therein to precipitate high boilingpoint impurity from the superheated portion of the feed mixture, and thefeed for the low pressure section comprises the liquid withdrawn from-the conglomerator through the conduit 82.

In the embodiment of the invention shown in FIGURE 7 of the drawings,the expansion valve l18 functions to expand the feed mixture toanintermediate pressure above the pressure existing in the high pressuresection 30, and the effluent from the expansion valve 18 includingliquid and vapor is conducted by the conduit 19 to a phase separator110. Vapor is withdrawn from the separator 110 and fed by conduit 111 tothe nozzle of an injector 112 discharging into the bottom of the liquidreceiving chamber 83 of the conglomerator 80. A stream of high boilingpoint fraction is withdrawn from the pool 35 of the high pressuresection 30 and conducted by a conduit 113 to the inlet of the injector112. The injector 112 may be similar to the injector 101 shown in FIGURE6 and functions to introduce liquid high boiling point fraction into theconglomerator against the head pressure of the liquid in the chamber 83.Flowing through the nozzle of the injector, the stream of vapor 4atintermediate pres sure is expanded to about the pressure existing in thehigh pressure section 30. Liquid is withdrawn from the separator 110,expanded in a valve 114 to the pressure existing in the high pressuresection 30, and introduced into a second phase separator115. Vapor iswithdrawn from the phase separator 115 by conduit 116 and introducedinto the conglomerator adjacent the bottom of the liquid receivingchamber 83, while liquid in the phase separator is withdrawn therefromby a conduit 1'17 and fed thereby to filters 43 or 44 depending upon theposition of switching valves 41 and 42. Liquid is withdrawn from theconglomerator by a conduit 118` and fed to a vessel 119 wherein -a poolof liquid 120 is maintained, the vessel may ybe provided with a device121 for indicating the level of the liquid therein and the conduit 1'18also conducts vapor from the vessel 119 to the conglomerator. Liquid iswithdrawn fro-m the vessel by a conduit 122 and is merged with theliquid in the conduit 117 for flow through the filters and adsorbers.from the dome of the conglomerator by a conduit 123 and introduced intothe high pressure section 30 of the fractionating column. The remainingportion of the gaseous feed mixture, which may comprise superheatedvapor yfrom the expansion engine 14, is conducted by the .conduit 16 andintroduced into the conglomerator 80 adjacent the bottom of the liquidreceiving chamber 83. In this cycle the portion of the feed mixture invapor phase, which may comprise efliuent from the expansion engine 14and vapor withdrawn from the phase separators and 115 as shown, isintermixed in the conglomerator with liquid high boiling point fractionfrom the high pressure section substantially completely free of highboiling point impurity. This performance is obtained since the vaporfrom the conglomerator in conduit 123 is substantially free of highboiling point impurity and comprises the feed for the high pressuresection of the column. The liquefied portion of the feed mixture fromthe phase separator and liquid withdrawn from.y the conglomeratorincluding substantially the total high boiling point impurity of thefeed mixture in conduits 16 and 116, are merged land passed throughlfilters and adsorbers prior to introduction into the low pressuresection 32 as feed. The

Vapor is withdrawn Y boiling point fraction.

9 vessel 119 provides an arrangementfor controlling the ow of liquidthrough the conduit 117 and into the filters and adsorbers.

In the cycle shown in FiGURE 8 o-f the drawings, the superheated vaporfrom the expansion engine 14 is conducted by the conduit 1,6 to anextension 124 of the high pressuresection 30. The partly liquefiedgaseous mixture downstream of the expansion valve 18 is fed by ltheconduit 19`to -a phase separator 125 having a vapor outlet conduit 126feeding theextension 124 and a liquid outlet conduit 127 connected tothe filters 43 and 44 through the switching valves 41 and 42. Theextension 124 of the high pressure section 30 retains a pool 128 ofliquid high boiling point fraction, the depth of the pool beingdetermined by the location of alliquid withdrawal conduit 129 connectedto the conduit 127. The extension 124 may also include a plurality oftrays such as, trays 130 and 131 positioned above the pool 128 and belowthe lowermost tray 34 of the high pressure section 30. 'Ihe trays 130and 131 are of the sieve type provided with openings of a diameterlarger than the openings in sieve type fractionating trays, such asabout one-half inch in diameter for example. In operation of thisembodiment, vapor portion of the feed mixture such as superheated vaporfrom the expansion engine and vapor from the separator `12S, is fed intothe extension 124 adjacent the bottom of the pool 128 wherein highboiling point impurity is precipitated and concentrated in the liquidhigh Vapor flows upwardly from the pool 128 and through the enlargedopenings in the trays 130 and 131 in intimate contact with downwardlyflowing liquid. High boiling point impurity that may flow upwardly withthe vapor is substantially completely precipitated and deposits aroundthe periphery of the openings in the trays 130 and 131 with the resultthat vapor entering the high pressure section 30 is substantiallycompletely free of high lboiling point impurity. High boiling pointimpurity deposits are dissolved by liquid flowing downwardly through theopenings of the trays 130 and 131 and substantially the total highboiling point impurity of the vapor portion of the feed mixture isconcentrated in the liquid of the pool 128. Liquid gaseous mixture fromthe separator 125, containing precipitated and dissolved high boilingpoint impurity, and liquid withdrawn from the pool 128, also containingprecipitated and dissolved high boiling point impurity, are merged,passed through one of the filter-adsorber combinations and fed,substantially free of high boiling point impurity, into the low pressuresection wherein the separation is completed producing liquid highboiling point component and gaseous low boiling point component. Ifdesired the extension 124 may comprise aseparate vessel unattached tothe fractionating column except for conduits conducting liquid from thebottom of the high pressure section to the top of the extension andvapor from the top of the extension to the bottom of the high pressuresection. When it is not possible to transfer liquid under the influenceof gravity a transfer pump may be employed Ior an ejector system similarto the arrangementyof FIGURE 7 may be used. In the latter case, theejector 112 could be located adjacent the upper end of the extension todischarge liquid therein above the trays 130 and 131.

While the various embodiments of the invention have been described inthe environment of a fractionating operation in which a portion of thefeed mixture may be at a temperature Within the superheat region, itwill be appreciated that certain novel features of the present inventionprovide unobvious advantages in aiding in the removal of high boilingpoint impurities from feed mixtures which may be below the superheatregon such as at saturation temperature. For example, in the embodimentof the invention shown in FIGURE 7, when product is not withdrawn inliquid phase adequate refrigeration may be obtained without theexpansion engine 14 and the valve 15 may be closed to pass the totalfeed mixture through the 1o heat exchange device 12. In such case, thevapor portions of the feed mixture from the phase separators -110 and115 are intermixed with liquid high boiling point fraction in the`conglomerator providing gaseous mixture in/ vapor phase from theconglomerator substantially completely free of high boiling pointimpurity which comprises the feed for the high pressure section. Thusthe invention provides :an arrangement for obtaining more completeremoval of high boiling point impurity from the feed mixture in vaporphase by separating the liquid and vapor phase of the feed mixture andthen mixingthe vapor portion with a liquid substantially 'free of highboiling point impurity, which liquid may include components of the feedmixture. Moreover, although the cycles disclosed and described above areof the type in which substantially the total high boiling point impurityin the feed mixture is removed from the cycle by means of filters andadsorbers, it is to be expressly understood that the principles of thepresent invention may be employed with cycles including switching heatexhange zones for removing the major portion of high boiling pointimpurities from the feed mixture. `In cycles employing switching heatexchange zones, particles of precipitated high boiling point impuritybecome entrained in the feed mixture and are passed into the cycledownstream of lthe heat exchange zones and collect in a cold portion ofthe cycle requiring eventual defrosting. By treating the cold feedmixture downstream of the heat exchange zones in accordance with theprinciples of the present invention the total high boiling pointimpurities may be substantially completelyV removedfrom the cycle.

Although several embodiments of the present invention have beendisclosed and described herein, it is to be expressly understood thatvarious changes'and substitutions may be made therein without departingfrom the spirit of the invention as well understood by those skilled inthe art. For example, although the invention has been described in theenvironment of separation of air it is to be expressly understood thatthe invention may be employed in fractionating cycles designed forseparating other gaseous mixtures. In addition, although in each of thedisclosed cycles the expansion engine is fed with a side stream ofgaseous feed mixture it is within the scope of the present invention tofeed the expansion engine with a separate stream of gaseous mixtureunder a pressure different from the pressure of the remaining portion ofthe feed mixture. Reference therefore will be had to the :appendedclaims for a definition of the limits of the invention.

What is claimed is:

1. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures` including high boilingpoint impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing liquid high boiling point fraction .and gaseous lowboiling point fraction and in which liquid high boiling point fractionis fed to a low pressure fractionating zone wherein the separation iscontinued producing liquid high boiling point product and gaseous lowboiling point product, which method comprises providing a stream ofcompressed gaseous mixture and passing the stream of compressed gaseousmixture in heat exchange effecting relation with cold product of theoperation to cool the stream. of gaseous mixture to a relatively lowpredetermined temperature such that liquid will not form in an ensuingexpansion step, expanding the cool stream of gaseous mixture toarelatively low pressure and further cooling the gaseous mixture withinthe superheat region, providing liquid material Vincluding components ofIthe gaseous mixture, intermixing the stream of expanded gaseous mixturewith the liquid material to cool the expanded gaseous mixture to atleast [its saturation] the precipitation temperature of the high boilingpoint impurity at the existing .pressure and sepl arating the resultingintermixture to provi-de a [saturated] vapor portion and a liquidportion, feeding [saturated] vapor portion to the high pressurefractionating zone, forming a lluid stream including the liquid portionof the intermixture and substantially the total high boiling pointimpurity of the stream of gaseous mixture, and paing the fluid streamthrough lter and adsorber zones and then to the low pressurefractionating zone, the fluid stream including the total liquid highboiling point fraction fed to the low pressure fractionating zone.

2. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing liquid high boiling point fraction and gaseous lowboiling point fraction and in which liquid high boiling point fractionis fed to a low pressure fractionating zone wherein the separation iscontinued producing liquid high boiling point product and gaseous lowboiling point product, which method comprises providing a stream ofcompressed gaseous mixture and passing the stream of compressed gaseousmixture in heat exchangeeffecting relation with cold product of theoperation to coolV the stream of gaseous mixture to a relatively lowpredetermined temperature such that liquid will not form in an ensuingexpansion step, expanding the cool streamY of gaseous mixture to arelatively low pressure and further cooling the gaseous mixture withinthe superheat region, providing liquid material including components ofthe gaseous mixture, intermixing the stream of expanded gaseous mixturewith the `liquidmaterial to cool the expanded gaseous mix-ture to atleast [its saturation] the precipitation temperature of the high boilingpoint impurity -at the existing pressure and separating lthe resultingintermixture to provide a [saturated] vapor portion and a liquidportion, feeding [saturated] vapor portion to the high pressurefractionating zone, forming a lluid stream consisting of the liquidportion of the intermixture and liquid high boiling point fractionwithdrawn from the high pressure fractionating zone, and passing the uidstream through filter and adsorber zones and then to the low pressurefractionating zone, the liquid high boiling point fraction of the uidstream comprising the total liquid high boiling point fraction fed tothe low pressure fractionating zone.

3. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures i11- cluding high boiling point impurity,in which operation compressed and cooled gaseous mixture is fed to ahigh pressure fractionating zone wherein the mixture undergoespreliminary separation producing a liquid high boiling point fractionand `a gaseous low boiling point fraction and in which liquid highboiling point fraction is fed to a low pressure fractionating zonewherein the separation is continued producing liquid high boiling pointproduct and gaseous low boiling point product, which method comprisesproviding a rst stream of compressed gaseous mixture and passing the rststream of compressedgascous mixture in heat exchange electing relationwith product of the operation to cool the first stream of gaseousmixture to a relatively' low predetermined temperature such that liquidwill not form in an ensuing expansion step, expanding the cool firststream of gaseous mixture to a relatively low pressure and furthercooling the stream to Within the superheat region, providing a secondstream of compressed gaseous mixture and passing the second stream ofcompressed gaseous mixture in heat exchange effecting relation withproduct of the operation to cool the second Istream of gaseous mixtureto a temperature lower than the predetermined temperature, expanding thecool second stream of gaseous mixture to the relatively low pressure andpartially liquefying the second stream,- intermixing the expanded rststream of gaseous mixture and the expanded second l2 stream of gaseousmixture to cool the first stream of gaseous mixture to at least [itssaturation] -ihe precipitation temperature of the high boiling pointimpurity at the existing pressure and separating the resulting interfmixture to provide a [saturated] vapor portion and a liquid portion,feeding the [saturated] vapor portion to .the high pressurefractionating zone, conducting the liqluid portion and liquid highboiling point fraction from the high pressure fractionating zone throughlter and adsorber zones and then to the low pressure fractionating zone,the liquid high boiling point fraction fed to the iilter and adsorberzones comprising the total liquid high boilling point fraction fed tothe low pressure fractionating zone.

4. Method of separating in a lo-w temperature fractionating operationcomponents of gaseous mixtures including highfboiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing a liquid high boiling point fraction land a gaseouslow boiling point fraction and in which liquid high boiling pointfraction is fed to a low pressure fractionating zone wherein theseparation is continued producing liquid high boiling point productVYand gaseous low boiling point product, which method comprisesproviding a first stream of compressed gaseous mixture and passing thefirst stream of compressed gaseous mixture in heat exchange effectingrelation with product of the operation to cool the irst stream ofgaseous mixture to a relatively low predetermined temperature such thatliquid will not form in an ensuing expansion step, expanding the coolrst stream of gaseous mixture to a relatively low pressure and furthercooling the stream to within the superheat region, providing a secondstream of compressed gaseous mixture and passing the seco-nd stream ofcompressed gaseous mixture in heat exchange eecting relation withproduct of the operation to cool the second stream of gaseous mixture toa temperature lower than the predetermined temperature,l expanding thecool second stream of gaseous mixture to the relatively low pressure andpartially liquefying the second stream, intermixing the expanded rststream of gaseous mixture and the expanded second stream of gaseousmixture to coo-l the rst stream of gaseous mixture to at least [itssaturation] the precipitation .temperature of the high boiling pointimpurity at the existing pressure and separating the resultingintermixture to provide a [saturated] vapor portion and a liquidportion, feeding the [saturated] vapor portion and the liquid portion tothe high pressure fractionating zone, withdrawing liquid includingliquid high boiling point fraction from the high pressure fractionatingzone, passing withdrawn'liquid through filter and adsorber zones andthen to the low pressure fractionating Zone, the liquid high boilingpoint fraction passed through the lter and adsorber zones comprising thetotal liquid high boiling point fraction passed to the low pressurefractionating zone.

5. Method of separating 4in la low temperature fractionating operation`components of gaseous mixtures including high boiling point impurity,in which operation compressed and cooled gaseous mixture is fed to ahigh pressure fraotionating zone wherein the mixture undergoespreliminary separation producing a liquid high boiling point fractionand a gaseous low boiling point fraction and in which liquid highboiling point fraction is fed to a low pressure fractionating zonewherein the separation is continued producing liquid high boiling pointproduot and gaseous low boiling point product, which method comprisesproviding a rst stream of compressed gaseous mixture and passing thelrst stream of compressed gaseous mixture in heat exchange effectingrelation with product of the operation to cool the rst -stream ofgaseous mixture to a relatively low predetermined temperature such thatliquid will not form in an ensuing 13 expansion step, expanding the coolfirst stream of gaseous mixture to a relatively low pressure and furthercooling the stream to within the superheat region, providing a secondstream of compressed gaseous mixture and passing the second stream ofcompressed gaseous mixture in heat exchange effecting relation withproduct of Ithe operation to cool the second stream of gaseous mixtureto a tem-V perature lower than the predetermined temperature, expandingthe cool second stream of gaseous mixture to the relatively low pressureand partially liquefying the second stream, intermixing the expandedfirst stream of gaseous mixture and the expanded second stream ofgaseous mixture to cool the first stream of gaseous mixture to at least[its saturation] the precipitation temperature ofthe high boiling pointimpurity at the existing pressure `and separating the resultingintermixture to provide a [saturated] vapor portion and a liquidportion, feeding the [saturated] vapor portion of the high pressurefractionating zone, withdrawing liquid high boiling point fraction fromthe high pressure fractionating zone, combining withdrawn liquid highboiling point fraction and the liquid portion of the intermixture toform a composite stream, Iand passing the composite stream throughfilter and adsorber zones and then to 4the low pressure fractionatingzone.

6. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing liquid high boiling point fraction and gaseous lowboiling point fraction and in which liquid high boiling point fractionis fed to a low pressure fractionating zone wherein the separation iscontinued producing liquid high boiling point product and gaseous lowboiling point product, which method comprises providing a stream ofcompressed gaseous mixture and passing the stream of compressed gaseousmixture in heat exchange effecting relation with cold product of theoperation to cool the stream of gaseous mixture to a relatively lowpredetermined temperature such that liquid will not form -in an ensuingexpansion step, expanding the cool stream of gaseous mixture to arelatively low pressure and further cooling the gaseous mixture withinthe super-heat region, intermixing the stream `of expanded gaseousmixture with liquid high boiling point fraction to cool the expandedgaseous mixture to at least .[its saturation] the precipitation temperafturer of the high boiling point impurity at the existing pressure andseparating the resulting intermixture to provide a [saturated] vaporportion and a liquid portion, feeding [saturated] vapor portion to thehigh pressure fractionating zone, and passing the liquid portion throughfilter and adsorber zones and then to the low pressure fractionatingzone.

7. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed `and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture under-I goes preliminaryseparation producing a liquid high bo-iling point fraction and a gaseouslow boiling point fraction and in which liquid high boiling pointfraction is fed to a low pressure fractionating zone wherein theproviding a 4second stream of compressed gaseous mixture and passing thesecond stream of compressed gaseous mixture in heat exchange leffectingrelation with product of the operation to cool the second stream ofgaseous mixture to a temperature lower than the predeterminedtemperature, expanding the cool second stream of gaseous mixture rto therelatively low pressure and partially liquefying the second stream,separating the expanded second stream .into a vapor portion and a liquidportion, intermixing the vapor portion of the expanded `second streamand the expanded first stream with liquid high boiling point fraction-to cool the first stream of expanded gaseous mixture to at `least [itssaturation] the precipitation temperature of the high boiling pointimpurity at the existing pressure and separating the resultingintermixture to provide la [saturated] Vapor por-tion and a liquidportion, feeding the [saturated] vapor portion to the high pressurefractionating zone, and passing the liquid portion of the second streamof gaseous mixture and the liquid portion of the intermixture throughfilter and adsorber zones and then to the low pressure fractionatingzone.

8. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing a liquid high Vboiling point fraction and a gaseouslow boiling point frac- -tion and in which Iliquid high boiling pointfraction is fed to a low pressure fractionating zone wherein theseparation is continued producing liquid high boiling point product and"gaseous lowV boiling point product, which method comprises providing afirst stream of compressed gaseous mixturev and passing the first streamof compressed gaseous mixture in heat exchange effecting relation withproduct of the operation to cool the rst stream of gaseous mixture to arelatively low predetermined temperature such that liquid will not formin an ensuing expansion step, expanding the cool first stream of gaseousmixture to a relatively low pressure and further cooling the stream towithin the superheat region, providing a second stream of compressedgaseous mixture and passing the second stream of lcompressed gaseousmixture in heat exchange effecting relation with product of theoperation to cool the second stream of gaseous mixture to a temperaturelower than the predetermined temperature, expanding the cool secondstream of gaseous mixture to the relatively low pressure'and partiallyliquefying the second stream, inter-mixing the first stream of expandedgaseous mixture with gaseous mixture of the second stream of expandedgaseous mixture and liquid high boiling point fraction to cool the firststream iof expanded gaseous mixture to at least [its saturation] theprecipitation temperature of the high boiling point impurity at theexisting pressure and separating the resulting intermixture to provide a[saturated] vapor portion and a liquid portion, feeding the [saturated]vapor por` Y tion to the high pressure fractionating zone, andconducting the liquid portion through filter and adsorber zones vandthen to the low pressure fractionating zone.

9. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fedto a highpressure fractionating zone wherein the mixture under- -goes preliminaryseparation producing a liquid high boiling point fraction and a gaseouslow boiling point @fraction and in which liquid lhigh boiling pointfraction is fed to a low pressure fractionating zone `wherein theseparation is continued producing liquid high boiling point product andgaseous low boiling point product, which method comprises providing afirst stream of compressed gaseous mixture and passing the first streamof compressed gaseous mixture in heat exchange effecting relation withthe second stream of compressed gaseous mixture in heat,

exchange effecting relation with product of the operation to cool thesecond stream of gaseous mixture to a temperature lower than thepredetermined temperature, ex-y panding the cool second stream ofgaseous mixture to the relatively low pressure and partially liquefyingthe second stream, intermixing the first stream of expanded gaseousmixture with the second stream of expanded gaseous mixture and liquidhigh boiling point lfraction to cool the first stream of expandedgaseous mixture to at least [its saturation] the precipitationtemperature of the high boiling point impurity at the existing pressureand separating the resulting intermixture to provide a [saturated] vaporportion and a liquid portion, :feeding the [saturated] vapor portion tothe high pressure fractiona-ting zone, and conducting the liquid portionthrough filter and adsorber zones and then to the low Ipressurefractionating zone, theliquid high boiling point fraction of theintermixture comprising the total high hoiling point fraction fed to thelow pressure fractionating zone.

l0. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high iboiling pointimpurity, inwhich operation compressed and cooled gaseous mixture is fed to a `highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing -liquid lhigh boiling point fraction and gaseouslow hoiling point fraction and in which liquid high fboiling pointfraction is fed to a lowpressure fractionating zone wherein theseparation is continued producing liquid high 'boiling point product andgaseous low boiling point product, which method comprises providing astream of compressed' gaseous mixture and passing the stream ofcompressed `gaseous mixture in heat exchange effecting. relation withcold product of the operation to cool the stream of gaseous mixture to arelatively low predetermined temperature such that liquid will not formin an ensuing expansion step, expanding the cool stream of gaseousmixture yto a-relatively low pressure and further cooling the -gaseousmixture within the superheat region, passing the stream of expandedgaseous mixture to an intermixing zone, employing energy of the expandedgaseous mixture to conduct liquid high 'boiling point fraction from thehighpressure fractiouating zone to the intermixing zone to cool theexpanded gaseous mixture to a least [its saturation] the precipitationtemperature of the high boiling point impurity at the existing pressure,withdrawing [saturated] vapor from the intermixing zone and feeding[saturated] vapor Ito the high pressure fractionating zone, withdrawingliquid from the intermixing zone and passing the liquid through lter andadsorber zones and then to the low pressure ractionating zone.V

ll. Method of separating in a low temperature rfractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes preliminaryseparation producing a liquid high hoi]- ing point `fraction and agaseous low boiling point fraction and in which liquid high boilingpoint fraction is fed to a low pressure fractionating zone wherein theseparation is continued producing liquid high lboiling point product and`gaseous low boiling point product, which method comprises providing afirst stream of compressed gaseous mixture and passing the first streamof compressed gaseous mixture in heatexchange effecting relation withproduct of the operation to cool the first stream of gaseous mixture toa relatively low predetermined temperature such that liquid will notform in an ensuing expansion step, expanding the cool tirst stream ofgaseous mixture to a relatively low pressure and further cooling thestream to within the superheat region, providing a second stream ofcompressed gaseous mixture and passing Ithe second ,stream of compressedgaseous mixture in heat exchange Vapor from the intermixing zone andfeeding the [saturated] Vapor tothe high pressure fractionating zone,withdrawing liquidvfrom the intermixing zone and conducting such liquidthrough filter and adsorber zones and then to the low pressurefractionating zone.

12. Method lof separating in a low temperature fractionating operationcomponents of gaseous mixtures including high fboiling point impurity,in which operation compressed and cooled gaseous mixture is fed to ahigh pressure ractionating zone wherein the mixture undergoespreliminary separation producing a liquid high boiling point fractionand a gaseous low hoiling point fraction and in which liquid highboiling point fraction is fed to a low pressure fractionating zonewherein the separation is continued producing liquid high boiling pointproduct and gaseous low hoiling point product, which method comprisesproviding a first stream of compressed gaseous mixture and passing theirst stream vof compressed gaseous mixture in heat exchangeeifectinglrelation with product of the operation to lcool the firststream 'of gaseous mixture to a relatively low predetermined temperaturesuch that liquid will not form in an ensuing expansion step, expandingthe cool rst stream of gaseous mixture to a relatively/ low pressure andfurther cooling the stream t0 within the superheat region, providing asecond stream of compressed gaseous mixture and passing the secondstream relation with product of the operation to cool the second streamof `gaseous mixture to a temperature lower than the predeterminedtemperature, expanding the cool second stream of gaseous mixture to anintermediate pressure above the relatively low pressure and partiallyliquefying the second stream, separating the expanded second stream intoan intermediate pressure vapor portion and an intermediate pressureliquid portion, expanding the intermediatepressure liquid portion to therelatively low pressure and separating the expanded intermediatepressure liquid portion into a low pressure vapor `portion and a lowpressure liquid portion, inter-mixing the intermediate pressure vaporportion and the low pressure vapor portion of the expanded second streamand the expanded first stream with liquid high boiling point fraction tocool the first stream of expanded gaseous mixture to at least [itssaturation] the precipitation temperature of the high boiling pointimpurity at the existing pressure and separating the resultingintermixture to provide a [saturated] vapor portion and a liquidportion, feeding the [saturated] vapor portion to the high pressurefractionating zone, passing the low pressure liquid portion and theliquid portion of the intermixture through filter and adsorber zones andthen to the low pressure fractionating zone.

13. Method of separating in a low temperature fractionating operationcomponents of gaseous mixtures including high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture under- 17 goespreliminary separation producing a liquid high boil ing point fractionand a gaseous low boiling point fracl tion and in which liquid highboiling point fraction is fed to a low pressure fractionating zonelwherein the separation is continued producing liquid high boilingpointproduct and gaseous low-boiling point product, which methodcomprises providing a first stream of compressed gaseous mixture andpassing the first stream of comp-ressed gaseous mixture in heat exchangeeffecting relation with product of the operation to cool the firststream of gaseous mixture to a relatively low predetermined temperaturesuch that liquid will not form in an ensuring expansion step, expandingthe cool first stream of gaseous mixture to a rel-atively low pressureand further cooling the stream to within the superheat region, providinga second stream of compressed gaseous mixture and passing the secondstream of compressed gaseous mixture in heat exchange eifecting relationwith product of the operation to cool the second stream of gaseousmixture to a.y temperature lower than the predetermined temperature,expanding the cool second stream of gaseous mixture to an intermediatepressure above the relatively low pressure and partially liquefying thesecond stream, separating theL expanded second stream into anintermediate pressure vapor portion and an intermediate pressure liquidportion, expanding the intermediate pressure liquid portion to therelatively low pressure and sepiarating the expanded intermediatepressure liquid portion into a low pressure vapor portion and la lowpressure liquid portion, feeding the intermediatepressure vapor portionand the low pressure vapor portion of the expanded second stream and theexpanded first stream to an intermixing zone and utilizing energy ofexpanded gaseous mixture to conduct liquid high boiling point fractionfrom the high pressure fractionating zone to the intermixing zone,withdrawing [saturated] vapor from the intermixing zone and feeding such[saturated] vapor to the high pressure fractionating zone, withdrawingliquid from the intermixing zone and conducting such liquid and the lowpressure liquid portion through filter and adsorber zones and then tothe low pressure fractionating zone. f

14. Method of separating in a low temperature fractionating operationcomponents of gaseous mixturesincluding high boiling point impurity, inwhich operation compressed and cooled gaseous mixture is fed to a highpressure fractionating zone wherein the mixture undergoes prelirninaryseparation producing a liquid high boiling point fraction and a gaseouslow boiling point fraction and in which liquid high boiling pointfraction is fed to a low pressure fractionating zone wherein theseparation is continued producing liquid high boiling point product andgaseous low boiling point product, which method comprises providing afirst stream of compressed gaseous mixture and passing the first streamof compressed gaseous mixture in heat exchange eifecting relation withproduct of the operation to cool the first stream of gaseous mixture toa relatively low predetermined temperature such that liquid willV notform in an ensuing expansion step, expanding the cool first stream ofgaseous mixture to a relatively low pressure and further cooling thestream to within the superheat region, providing a second stream ofcompressed gaseous mixture and passing the second stream of compressedgaseous mixture in heat exchange effecting relation with product of theoperation to cool the second stream of gaseous mixture to a temperaturelower than the predetermined temperature, expanding the cool secondstream of gaseous mixture to the relatively low pressure and partiallyliquefying the second stream, separating the expanded second streamvinto a vapor portion and a liquid portion, passing the vapor portionofthe expanded second stream and the expanded first stream with liquidhigh boiling point fraction to a liquid receiving zone in vaporcommunication with the high pressure fractionating zone to 18' intermixthe vapor portion and the second stream of gaseous mixture with liquidin the liquid receiving zone, withdrawing liquid from the liquidreceiving zone, passing liquid withdrawn from the liquid receiving zoneand the liquid portion of the second stream of gaseousmixlture throughiilter and adsorber zones and then to the low pressure fractionatingzone.

l5. Method of separating air in a low temperature fractionatingoperation to produce liquidoxygen product, in which operation compressedand cooled air is fed to a high pressure fractionating zone wherein themixture undergoes preliminary separation producing liquid high boilingpoint fraction Iand gaseous low boiling point fraction and in whichliquid high boiling point fraction is fed to a low pressurefractionating zone wherein =the separation is continued producing liquidoxygen product and gaseousy lowfboillng .point product, which methodcomprises providing a stream of compressed air and passing the stream ofcompressed air in heat exchange eiecting relation with gaseous lowboiling point product of the operation to cool the stream of lair to arelatively low predetermined temperature such that liquid will not formVin an ensuing expansion step, work expanding the cool stream of air toa relatively low pressure and further cooling the gaseous mixture withinthe superheat region, providing liquid material including components` ofair, intermixing the stream of expanded air with the liquid material tocool the expanded air to at least [its saturation] the precipitationtemperature of the high` boiling point impurity at the existing pressure`and separating the resulting intermixture to provide a [saturated]vapor portion and la* liquid portion, yfeeding [saturated] vapor portionto the high pressure -fractionating zone, forming a iluid streamincluding substantially the high boiling point impurity of 'the air andpassing the iiuid stream through ,lter and adsorber zones and then tothe `low pressure fraetionating zone, the iluid stream including thetotal liquid high boiling point fraction fed to the low pressurefractionating zone, and. withdrawing liquid oxygen from the low pressurefractionating zone. p t

16. Method of separating air in `a. low temperature fractionatingoperation to produce liquid` oxygen, in which operation compressed'iandcooled air is fed to a high pressure fractionating zone wherein themixture undergoes preliminary separation producing a liquid high boilingpoint fraction and a gaseous low boiling point fraction .and in whichliquid high boiling point fraction is fed -to a low pressurefractionating zone wherein the separation is continued producing liquidoxygen product Iand gaseous low boiling point product, which methodcomprises providing la lirst stream of compressed air `and passing thefirst stream of compressed air in heat exchange effecting relation withgaseous low boiling point product of the operation to cool the fir-ststream of air to a relatively low predetermined temperature such thatliquid will-not form in an ensuing expansion step, work expanding thecool yfirst stream of air to a relatively low pressure and furthercooling the air to within the superheat region, providing 4a secondstream of compressed air Iand passing the second stream of compressedair in heat exchange eiecting relation with gaseous low boiling pointproduct of the operation to cool the second stream of air to atemperature lower than the predetermined temperature, expanding the coolsecond stream of t air to the relatively low pressure and partiallyliquefying the second stream, intermixing the rst stream of expanded airwith at least a portion of the second stream of expanded air and liquidhigh boiling point tt-nacti'on to lcool the first stream of expanded airto at least [its saturation] the `precipitation temperature of vthe highboiling point impurity at the existing pressure and separating theresulting intermixture to. provide ,a

[saturated] vapor portion and -a liquid portion, Ifeeding the[saturated] Vapor portion to the high pressure fractionating zone, andconducting `the liquid portion through 19 filter and adsorber zones andthen to the low pressure fractionating zone.

17. Apparatus for separating components of gaseous mixtures comprisingIa two-stage fractionating column including a high pressurefractionating zone wherein the mixture undergoes preliminary separationproducing liquid high boiling point fraction and gaseous low boilingpoint fraction and a low pressure fractionating zone wherein theseparation is continued producing liquid high boiling point productandgaseous low boiling point product, means providing a stream ofcompressed gaseous mixture and passing the stream of compressed gaseousmixture in heat exchange effecting relation with cold product of theractionating column to cool the stream of gaseous mixture to arelatively low predetermined temperature such that liquid will not formin an ensuing expansion step, a work expansion engine for expanding thecool stream of gaseous mixture to a relatively low pressure and furthercooling the gaseous mixture within the superheat region, means providingliquid material including components of the gaseous mixture, meansintermixing the stream of expanded gaseous mixture with the liquidmaterial to cool the expanded gaseous mixture to at least [itssaturation] the precipitation temperature of 'the high boiling pointimpurity lat the existing pressure pressure fractionating zone.

1,8. Apparatus'for separating components of gaseous mixtures comprisinga two-stage tfractionating column including -a high pressurefractionating zone wherein the mixture undergoes preliminary separationproducing liquid high boiling point yfraction and gaseous low boilingpoint fraction and a low pressure rractionating zone wherein theseparation is continued producing liquid high 'boiling point product andgaseous low lboiling point prod-A uct, means providing la stream ofcompressed gaseous mixture and passing the stream of compressed gaseousmixture in heat exchange effecting relation with cold product for thefractionating column to cool the stream of gaseous mixture to arelatively low predetermined temperature such that liquid lwill not'formin an ensuing expansion step, la work expansion` engine for expandingthe cool stream of gaseous mixture to a relatively low pressure and`further cooling the gaseous mixture within the superheat region, meansintermixing the stream of expanded gaseous mixture with liquid highboiling point fraction to cool the expanded gaseous mixture to at least[its saturation] the precipitation temperature of the high boiling pointimpurity at the existing pressure and separating the resultingintermixture to provide a [saturated] vapor portion Vand -a liquidportion, means feeding [saturated] vapor portion to the high pressurefractionating zone, and means passing the liquid portion through ltermeans and adsorber means and then to the low pressure fractionatingzone.

19. Apparatus for separating components of gaseous mixtures comprising atwo-stage tractionating column including a high pressure fractionatingzone wherein the mixture undergoes preliminary separation producing aliquid high boiling point Vfraction and gaseous low boiling pointfraction and a low pressure fractionating zone wherein the separation iscontinued producing liquid high boiling point product and gaseous lowboiling point product, means providing a first stream of compressedgaseous mixture and passing the first stream of compressed gaseousmixture in heat exchange effecting relation with product of thefractionating column to cool the first stream of gaseous mixture to arelatively low predetermined temperature such that liquid will not formin an ensuing expansion step, a work expansion engine for expanding thecool first stream of gaseous mixture to a relatively low pressure andfurther cooling the stream to Within the superheat region, meansproviding a second stream of compressed gaseous mixture yand passing theseoond stream of compressed gaseous mixture in heat exchange effectingrelation with product of the fractionating column to cool the seoondstream of gaseous mixture to a temperature lower than the predeterminedtemperature, means expanding the cool second stream of gaseous mixtureto the relatively low pressure and partially liquefying the secondstream, means intermixing the expanded first stream of gaseous mixtureand the expanded second stream of gaseous mixture to cool the iirststream of gaseous mixture to at least [its saturation] the precipitationtemperature of the high boiling point impurity at the existing pressureand separating the resulting intermixture to provide a [saturated] vaporportion and a liquid portion, means feeding the [saturated] vaporportion to the high pressure fractionating zone, and means conductingthe liquid portion and liquid high boiling point fraction yfrom the highpressure fractionating zone through iilter means and adsorber means andthen to the low pressure fractionating zone.

20. Apparatus for separating components of gaseous mixtures comprising'a two-stage fractionating column including a high pressurefractionating zone wherein the mixture undergoes preliminary separationproducing a liquid high boiling point fraction and gaseous low boilingpoint Ifraction and a low pressure fractionating Zone wherein theseparation is continued producing liquid high boiling point product andgaseous low boiling point product, means providing a -iirst stream offcompressed gaseous mixture and passing the first stream of compressedgaseous mixture in heat exchange effecting relation with cold product ofthe fractionating column to cool the first stream of gaseous mixture toa relatively low predetermined temperature such that liquid will notyform in an ensuing expansion step, a work expansion engine for ex- Ypanding the cool first stream of gaseous mixture to a relatively lowpressure and `further cooling the streamto within the superheat regi-on,means providing a second stream of compressed gaseous mixture andpassing the second stream of compressed gaseous mixture in heat exchangeeffecting relation with product of the fractionating column to cool thesecond stream olf gaseous mixture to a temperature lower than thepredetermined temperature, means expanding fthe cool seoond stream ofgaseous mixture to the relatively low pressure and partially liquefyingthe second stream, means intermixing the first stream of expandedgaseous mixture with the liquid portion of the second stream of expandedgaseous mixture and liquid high boiling point fraction to cool the firststream of expanded gaseous mixture to atleast [its saturation] theprecipitation temperature of the high boiling point impurity at theexisting pressure and separating the resulting intermixture to provide a[saturated] vapor portion and a liquid portion, means feeding the[saturated] vapor portion to the high pressure fractionating zone, andmeans liquid high boiling point fraction and a gaseous 10W boiling pointfraction and a low pressure fractioning zone wherein the separation iscontinued producing liquid high boiling point product and gaseous lowboiling point product, means providing a first stream of compressedgaseous mixture and passing the first stream of compressed gas- 21 eousmixture in heat exchange electing relation with product of thefractionating column to cool the rst stream of gaseous mixture to arelatively low predetermined temperature such that liquid will not formin an ensuing ex pansion step, a work expansion engine for expanding thecool tirst stream of gaseous mixture to a relatively low pressure andfurther cooling the stream to within the superheat region, meansproviding a second stream of compressed gaseous mixture and passing thesecond stream of compressed gaseous mixture in heat exchange eectingrelation with product of the fractioning column to cool the secondstream of gaseous mixture to a temperature lower than the predeterminedtemperature, means expanding the cool second stream of gaseous mixtureto the relatively low pressure and partially liquefying the secondstream, means separating the expanded second stream into a vapor portionand a liquid portion, means intermixing the vapor portion of theexpanded second stream and the expanded first stream with liquid highboiling point fraction to cool the first stream of expanded gaseousmixture to at least [its saturation] zhe precipitation temperature ofthe high boiling point impurity at the existing pressure and separatingthe resulting intermixture to provide a [saturated] vapor portion and aliquid portion, means feeding the [saturated] vapor portion to the highpressure fractionating zone, and means passing the liquid portion of thesecond stream of gaseous mixture and the liquid portion of theinterrnixture through ilter means and ad- ,fsorber means and then to thelow pressure fractioning zone.

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